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Flammable and Combustible Liquids
29 CFR 1910.106

Introduction

Since the advent of the industrial revolution, the use of non-water-based chemicals has increased dramatically. Due to this increase, the potential exposure to the hazards associated with these chemicals has also increased. This includes hazards to worker health as well as property.

One potential hazard is flammability. To prevent fires, hazardous liquids need special precautions taken for their storage, handling and use. Both the National Fire Protection Agency (NFPA) and the International Code Council (ICC) develop the Uniform Fire Code and have developed guidelines for the safe storage and use of flammable and combustible liquids. These guidelines are not mandatory unless a federal, state or local authority chooses to use them. On the contrary, the Occupational Safety and Health Administration (OSHA) has developed mandatory regulations for General Industry (29 CFR 1910.106), Construction Industry (29 CFR 1926.152) and Shipyard Industry (29 CFR 1915.36). For the purpose of this document, only the requirements of the General Industry will be discussed.

Flammable or Combustible?

To understand OSHA requirements for the safe storage of flammable and combustible liquids, we must begin by defining the two. A flammable liquid is any liquid having a flashpoint below 100° F (37.8° C) (except any mixture having components with flashpoints of 100° F (37.8° C) or higher, the total of which make up 99 percent or more of the mixture)(1910.106(a)(19)). Flammable liquids are categorized into three groups, as follows:

•Class IA

Liquids having flashpoints below 73° F (22.8° C) and having boiling points below 100°F (37.8°C) (1910.106(a)(19)(i)). Examples: Acetaldehyde, ethyl ether and cyclohexane.

•Class IB

Liquids having flashpoints below 73° F (22.8° C) and having boiling points at or above 100° F (37.8°C) (1910.106(a)(19)(ii)). Examples: Acetone, benzene and toluene.

•Class IC

Liquids having flashpoints at or above 73° F (22.8° C) and below 100° F (37.8°C) (1910.106(a)(19)(iii)). Examples: Hydrazine, styrene and turpentine.

A combustible liquid is any liquid having a flashpoint at or above 100° F (37.8° C) (1910.106(a)(18)). Combustible liquids are divided into two classes:

•Class II

Liquids having flashpoints at or above 100° F (37.8° C) and below 140° F (60° C), except any mixture having components with flashpoints of 200°F (93.3°C) or higher, the volume of which make up 99 percent or more of the total volume of the mixture (1910.106(a)(18)(i)). Examples: Acetic acid, naphtha and stoddard solvent.

•Class III

Liquids having flashpoints at or above 140°F (60°C) (1910.106(a)(18)(ii)). Class III liquids are subdivided into two subclasses:

•Class IIIA

Liquids having flashpoints at or above 140°F (60°C) and below 200°F, except any mixture having components with flashpoints of 200°F (93.3°C) or higher, the total volume of which make up 99 percent or more of the total volume of the mixture (1910.106(a)(18)(ii)(a)). Examples: Cyclohexanol, formic acid and nitrobenzene.

•Class IIIB

Liquids having flashpoints at or above 200°F (93.3°C) (1910.106(a)(18)(ii)(b)). Examples: Formalin and picric acid.

Per 1910.106(a)(18)(ii)(b) "Class IIIB liquids" shall include those with flashpoints at or above 200°F (93.3°C). This section does not cover Class IIIB liquids. Where the term "Class III liquids" is used in the section, it shall mean only Class IIIA liquids. (Class IIIB is used in this document for reference purposes only.)

*Note: When a combustible liquid is heated for use to within 30°F (16.7°C) of its flashpoint, it shall be handled in accordance with the requirements for the next lower class of liquids (1910.106(a)(18)(iii)).

The flashpoint and boiling point determine the class of a liquid. However, these should not be the only criteria used to determine the hazards of a liquid. Many other factors should also be considered for the proper use and storage of hazardous liquids. These factors include: ignitions temperature, explosive limits (LEL or UEL), vapor pressure, specific gravity and vapor density.

Safety Cans

One technique to reduce the hazards associated with flammable and combustible liquids is the use of safety cans. OSHA defines a safety can as ". . . An approved container, of not more than 5 gallons capacity, having a spring-closing lid and spout cover and so designed that it will safely relieve internal pressure when subjected to fire exposure" (1910.106(a)(29)). This definition allows a wide variety of containers to be considered safety cans. However, many local laws and insurance carriers require safety cans to be Factory Mutual (FM) or Underwriter Laboratory (UL) approved. These two organizations are nationally recognized independent testing laboratories to which manufacturers submit products for evaluation of their ability to meet safety requirements under intended use. Products that meet the requirements are given either a FM or UL product approval. Both laboratories are also recognized by OSHA. (See EZFacts® Document No. 100.)

In addition to the storage of flammable and combustible liquids in safety containers, 29 CFR 1910.106 limits the amount of liquid in a single container. The following chart shows what the allowable amounts of liquid are for each class of liquid.

There are exceptions to this rule:

• Medicines, beverages, foodstuffs, cosmetics, and other common consumer products, when packaged according to commonly accepted practices.

29 CFR 1910.106 also limits the total amount of a liquid kept outside of a cabinet or storage room. The quantity of liquid that may be stored outside of an inside storage room or a cabinet in any one fire area of a building cannot exceed:

•25 gallons of Class IA liquids in containers

•120 gallons of Class IB, IC, II or III liquids in containers

•660 gallons of Class IB, IC, II or III liquids in a single portable tank

The amount of liquid storage and location of cabinets is regulated. 1910.106 (d)(3) states, "Not more than 60 gallons of Class I or Class II liquids, nor more than 120 gallons of Class III liquids may be stored in a storage cabinet." Also, according to NFPA 304.3.2, not more than three (3) such cabinets may be located in a single fire area.

Flammable Storage Cabinet Requirements

Another fundamental means of fire protection is the use of flammable storage cabinets. The NFPA, OSHA and UFC require flammable cabinets to be designed and constructed to specific requirements. 1910.106(d)(3)(ii)(a) states that metal cabinet shall be constructed in the following manner:

•Bottom, top and sides of cabinet shall be at least No. 18 gauge sheet steel

•Cabinet must be doubled walled with 1½" airspace

•Joints shall be riveted, welded or made tight by some equally effective means

•Door shall have a three point latch

•Door sill shall be raised at least 2" above the cabinet bottom to retain spilled liquid within the cabinet

•Cabinet shall have a "FLAMMABLE—KEEP FIRE AWAY" legend

These regulations also provide an option for wood cabinets. 1910.106(d)(3)(ii)(b) states that wood cabinets shall be constructed in the following manner:

•Bottom, top and sides of cabinet shall be at constructed of exterior grade plywood at least 1" thick

•Plywood shall not break down or delaminate under fire conditions

•Joints shall be rabbeted and fastened in two directions with flathead wood screws

•When more than one door is used, they should have a rabbeted overlap of not less than 1"

•Doors shall be equipped with latches and hinges that are mounted to not lose their holding capacity when subjected to fire

•Door sill or pan shall be raised at least 2" above the cabinet bottom to retain spilled liquid within the cabinet

•Cabinet must have a "FLAMMABLE—KEEP FIRE AWAY" legend

In addition to the requirements listed above, the UFC (Uniform Fire Code) also requires self-closing doors. Most local authorities use one or more of these standards as a foundation for establishing local codes.

Fire Areas

OSHA does not provide a definition of a fire area in this standard. However, a fire area is defined by NFPA Code 30 (1.6.15) as, "An area of a building separated from the remainder of the building by construction having a fire resistance of at least 1 hour and having all communicating openings properly protected by an assembly having a fire resistance rating of at least 1 hour." The NFPA also provides a special provision for the grouping of flammable cabinets in an industrial facility. Because most industrial settings do not have walls or barriers within a facility, "In an industrial occupancy, additional cabinets may be located in the same fire area if the additional cabinets, or the group of not more than three (3) cabinets, is separated from the other cabinets or group of cabinets by at least 100 feet (30 m)." (4.3.2 Exception 1)

Commonly Asked Questions

Sources for More Information

National Fire Protection Association, Flammable and Combustible Liquids Code Handbook, Sixth edition, ed. Robert Benedetti, 1996.

United States Office of the Federal Register National Archives and Records Administration, 29 Code of Federal Regulations Parts 1900 to 1910, (Washington: GPO 1994).

National Institute of Occupational Safety & Health, Pocket Guide to Chemical Hazards, U.S. Department of Health and Human Services. (Washington: GPO 2005).

International Code Council

National Fire Protection Association

Occupational Safety and Health Administration (OSHA)

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